Because of a configuration in which light emitted from a light source is modulated by a light valve such as a liquid crystal panel, etc., and the modulated light is projected, a projection type video display needs to be provided with a high-intensity light source. For this, it is needed to prepare measures against heat generated from the high-intensity light source itself, or heat generated at a time that the light is absorbed by a polarizer of a liquid crystal panel or various kinds of optical components. From the past, an intake and exhaust are performed by rotating a cooling fan by a motor so as to release the heat to outside the video display (see Japanese Patent Laying-open No. 2001-222065).
Incidentally, in order to take in outside air into the video display for cooling, a filter is provided at an air-intake port for removing a dust in the outside air, and if this filter is clogged, an appropriate cooling control cannot be realized.